Laser net shape manufacturing using an adaptive toolpath deposition method

ABSTRACT

A method is disclosed for laser cladding a substrate, comprising providing the substrate; depositing a first determined variable bead width of a material along a toolpath upon the substrate; depositing a second adjacent determined variable bead width of a material along the toolpath which overlaps the first determined variable bead width of deposited material; continuing to deposit a plurality of overlapping predetermined adjacent variable bead widths of a material until a first material layer is complete; forming a second material layer by depositing a plurality of overlapping predetermined variable bead widths of a material on top of the first material layer; and continuing to deposit material layers on top of deposited material layers until the cladding is complete; wherein the variable bead width of the deposited material is controlled by a computer having a plurality of input parameters to maintain an approximately constant percent of bead width overlap.

FIELD OF THE INVENTION

This invention relates to a manufacture and repair procedure for a part,for example a turbine component such as a bladed disk (BLISK),compressor blade, or turbine blade.

BACKGROUND OF THE INVENTION

An aircraft gas turbine engine or jet engine draws in and compresses airwith an axial flow compressor, mixes the compressed air with fuel, burnsthe mixture, and expels the combustion gases through an axial flowturbine to power a compressor. The compressor includes a disk withblades projecting from its periphery. The disk turns rapidly on a shaft,and the curved blades draw in and compress air.

In current manufacturing practice, the compressor is made by forging thecompressor disk as a single piece with slots at the periphery. Thecompressor blades are individually cast or forged to shape with a rootsection termed a dovetail that fits into slots formed in the disk.Assembly is completed by sliding the dovetail sections of the bladesinto the slots in the disk. If a blade does not fit properly, fails, oris damaged during service, it may be readily replaced by reversing theassembly procedure to remove the blade, and providing a new blade.

Blades may also be formed integrally with the disk, in a combinationtermed a bladed disk or BLISK. This combination may also be known as anintegrally bladed rotor. The BLISK approach to manufacturing offers thepotential for increased performance through reduced weight. Such anarticle can be cast or forged as a large disk with an excess of metal atthe periphery. The blades are then machined from the excess metal,integrally attached to the disk. The final product is expensive toproduce, as it requires extensive high-precision machining operations.An error in machining even one of the blades may result in rejection andscrapping of the entire BLISK or an expensive and time consuming repair.

Replacement or repair of a damaged blade portion of the BLISK or turbineblade presents a difficult problem with this cast and machine or forgeand machine approach. If all or a portion of a blade breaks off fromimpact of a foreign body during operation, for example, the BLISKbecomes unbalanced. Damaged BLISKS may be repaired by welding excessmetal into the damaged area and machining the metal to form theappropriate shape, or by cutting out the damaged area and replacing thecut out material by diffusion bonding a new piece into the damaged area.However, such an approach is both expensive and may result in reducedperformance and durability.

A different approach to manufacture and repair BLISKS has been disclosedin U.S. Pat. No. 5,038,014, incorporated herein by reference. Thisapproach utilizes a laser cladding or welding technique that feedspowders into molten material on the surface to be repaired, whichproduces a layer of new material. By repeating this process in alayer-by-layer fashion, these layers are built upon one another to formnew parts or to repair damaged parts.

Past laser cladding techniques have resulted in imperfections andinclusions in the formed or repaired part resulting from lack ofcomplete fusion between successive layers or extensive porosity of thedeposited layers. These imperfections and inclusions are oftenassociated with complex geometry of the formed or repaired part.Therefore, a need exists to provide a layered fabrication technique thatsolves the problems associated with the past manufacture and repairtechniques.

Laser Net Shape Manufacturing (LNSM) provides an economical and highlyflexible method to form and restore BLISKS, compressor blades andturbine components. The LNSM technique is based on laser cladding,wherein a laser is used to create a 3D geometry by precisely claddingthin layers of metal powder on a base material.

LSNM may be used in the fabrication of new parts and the repair ofdamaged parts. A Computer Aided Design (CAD) model of a part to befabricated is uniformly sliced along the desired direction of materialbuildup. Powder is applied and fused along a tool path to create amaterial layer, layers are then built upon one another until the part isfabricated. Various tool paths have been used in applying the powders,the most common being a zigzag pattern or a stitch pattern, depending onwhether the material is forming an internal area or a surface area ofthe part. However, prior LSNM methods result in inclusions of fusionimperfections and porosity in newly fabricated or repaired parts,requiring that the part either be scrapped or further processed torepair the imperfections. In addition, past laser deposition methods forfabrication and repair have not focused on producing accurate shapes andgeometries.

Therefore, a need exists to develop an accurate LNSM method that reducesfusion imperfections and porosity that allows turbine componentsincluding BLISKS, compressor blades and turbine blades to bemanufactured and repaired.

SUMMARY OF THE INVENTION

In accordance with a first embodiment of the invention, a process forfabricating an article is disclosed that comprises the steps ofproviding a substrate, depositing a first determined variable bead widthof a material along a toolpath upon the substrate, depositing a secondadjacent determined variable bead width of a material along the toolpathwhich overlaps the first determined variable bead width of depositedmaterial, continuing to deposit a plurality of overlapping predeterminedadjacent variable bead widths of a material until a first material layeris complete; forming a second material layer by depositing a pluralityof overlapping predetermined variable bead widths of a material on topof the first material layer, and continuing to deposit material layerson top of deposited material layers until the cladding is complete. Thevariable bead width of the deposited material is controlled by acomputer having a plurality of input parameters to maintain anapproximately constant percent of bead width overlap.

In accordance with a second embodiment of the invention, a laser netshape manufacturing or repair method is disclosed that comprisesproviding a substrate, forming by laser cladding a first determinedvariable bead width of a material along a toolpath upon the substrate,forming by laser cladding a second adjacent determined variable beadwidth of a material along the tool path which overlaps the firstdetermined variable bead width, continuing to deposit overlappingpredetermined adjacent variable bead widths of a material until a firstmaterial layer is complete, forming by laser cladding a second powderlayer by depositing overlapping predetermined variable bead widths of amaterial on top of the first material layer, and continuing to depositmaterial layers on top of deposited material layers until the claddingis complete and a net shape article is manufactured or repaired. Thevariable bead width of the deposited material is controlled by acomputer having input parameters to maintain an approximately constantpercent of bead width overlap. A BLISK, compressor blade, turbine bladeor turbine component may be manufactured or repaired according to thissecond embodiment of the invention.

According to a specific embodiment of the invention, a method ofrepairing a BLISK, compressor blade, turbine blade or turbine componentis disclosed that comprises providing a damaged BLISK, turbine blade orturbine component and prepping the damaged BLISK, turbine blade orturbine component to form a substrate surface, depositing a firstdetermined variable bead width of a material along a toolpath upon thesubstrate, depositing a second determined variable bead width of amaterial along a toolpath that is adjacent the deposited firstdetermined variable bead width of a material and overlaps the firstdetermined variable bead width of the deposited material layer,continuing to deposit adjacent overlapping predetermined variable beadwidths of a material until a first material layer is complete, forming asecond material layer by depositing overlapping predetermined variablebead widths of a material on top of the first material layer, andcontinuing to deposit material layers on top of deposited materiallayers until the cladding is complete. The bead width of the depositedmaterial is controlled by a computer having input parameters to maintainan approximate constant percent of variable bead width overlap ofadjacent variable bead widths of material and each deposited variablebead with is varied. A BLISK, compressor blade, turbine blade, orturbine component may be manufactured or repaired in accordance with thespecific embodiment of the invention.

According to another embodiment of the invention, a method for lasercladding a substrate is disclosed that comprises providing thesubstrate, depositing at least one first determined variable bead widthof a material along a toolpath upon the substrate to form a firstmaterial layer, forming a second material layer by depositing at leastone variable bead width of a material on top of the first materiallayer, and continuing to deposit material layers formed by at least onevariable bead width of material on top of deposited material layersuntil the cladding is complete.

According to yet another embodiment of the invention, a laser net shapemanufacturing or repair method is disclosed that comprises providing asubstrate, forming by laser cladding at least one first determinedvariable bead width of a powder material along a toolpath upon thesubstrate to form a first material layer, forming by laser cladding asecond material layer by depositing overlapping predetermined variablebead widths of a powder material on top of the first powder layer, andcontinuing to deposit powder layers on top of deposited powder layersuntil the cladding is complete and a net shape article is manufacturedor repaired.

Other features and advantages of the present invention will be apparentfrom the following more detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the invention. Thescope of the invention is not, however, limited to this preferredembodiment

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a general LNSM deposition system.

FIG. 2 is a perspective view of an exemplary BLISK.

FIG. 3 is a block diagram of an embodiment of the Adaptive Tool PathDeposition Method.

FIG. 4 is an illustration of an exemplary damaged BLISK blade.

FIG. 5 is an illustration of a material build up upon an exemplarydamaged BLISK blade.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a Laser Net Shape Manufacturing (LNSM)method for fabricating and repairing articles such BLISKS, compressorblades, turbine blades, and compressor components that solves theproblems associated with the prior art. The LNSM technique is based onlaser cladding metal powders, wherein a laser is used to create a 3Dgeometry by precisely cladding thin layers of powder material on a basesubstrate using an adaptive toolpath deposition method. The adaptivetoolpath method includes providing a predetermined variable bead widthwithin a deposited layer. The base substrate may be a BLISK surface,such as BLISK compressor disk or a BLISK blade edge. Although specificembodiments discussed below are directed to BLISKS, the invention isequally applicable to the LNSM of other parts, including a variety ofturbine parts including compressor blades and turbine blades.

To form a shaped deposit by LNSM, the dimensions and overall geometry ofthe part or repair section are rendered in accordance with acomputer-aided design (CAD) description. The geometry of the repair mustbe described mathematically. Modeling of the shapes is achieved throughthe use of a CAD system, and from these representations, toolpaths aregenerated to drive the LNSM process.

In order to drive the LNSM's computer numerical control (CNC) system, atoolpath file is generated from commercial computer aided manufacturing(CAM) software containing commands that are understandable to the CNC.The commands are loaded into memory and executed. Typical commands aremove commands, which tell the CNC to move to a new point at a givenspeed, turn on/off the laser and powder flow. These commands are allembedded directly within the part program when it is created, and aretriggered at specific points in the program. Some parameters thatcontrol the process must be changed dynamically during the processing ofa part, including but not limited to laser power, tool velocity, powderfeed rate, and overlap ratio.

Many articles may be analyzed as being an assembly of sections or slicesparallel to each other. The article is then uniquely defined byspecifying the pattern of each section, that is, its shape and size, andthe position of each section, that is, its relationship to the adjacentsections. In such a manner, BLISK blades may be formed around thecircumference of a BLISK compressor disk. The pattern of each sectionmay be amenable to formation by a bead of deposited material, where abead is an elongated deposit typically formed by moving the substraterelative to a heat source. Where such is the case, the article may beformed by depositing a bead of a variable width, or several side-by-sidebeads of variable widths in the inventive manner as set out above, inthe shape of the pattern of a section, and then incrementing thedeposition apparatus upwardly by the bead height, thereafter depositinganother bead having the pattern of the next section and the requiredposition in relation to the previously deposited bead. During each pass,the laser welding deposition unit melts the upper portion of thepreviously deposited bead, or substrate in the first pass, and adds morematerial through its powder feed to form the overlying bead. The newlyadded material and the previously deposited bead partially intermix andsolidify together, ensuring a continuous, strong structure through thebeads substantially free of imperfections. The process is repeated asmany times as necessary to form the article.

A wide variety of shapes and sectional configurations may be made bythis approach. Solid figures are made by laying down beads of variablewidths above one another. Increased thickness is achieved by laying downseveral beads of variable widths in a side-by-side fashion in each layerin accordance with the invention as described above, and then addingmore beads above that layer. Parts of varying thickness are made bychanging the number of overlapping beads of variable widths in a layer.Hollow airfoil or other hollow shapes are made by depositing the bead inthe shape of the outer wall, and then depositing additional overlappingbeads on top of the other. Hollow sections with internal structure, suchas cooling passages, are made by adding internal ribs and the like toeach section, in addition to the outer walls. Virtually any shape can bedefined as a collection of beads, and the present approach has theversatility to make such a wide variety of shapes. Typically, aircraftengine applications include compressor blades, turbine blades, fanblades, tubes, and boxes, with the later having square, rectangular, orirregular cross sections.

The control of the deposition is accomplished by numericallycharacterizing the shape of the article such as a blade from drawings ora part prepared by more conventional methods such as machining. Once theshape of the part is numerically characterized, such as by a computeraided design (CAD) solid model of the article, the movement of the partor equivalently, the deposition head, is programmed using availablenumerical control computer programs to create a pattern of instructions,known as transfer functions, as the movement of the part during eachpass, and its lateral displacement between the passes. These developedtransfer functions maintain a determined variable bead width andconstant overlap of a deposited material in accordance with theinvention. The resulting article reproduces the shape of the numericalcharacterization very accurately, to net shape or near-net shapespecifications, including complex curves of an airfoil.

The LNSM method for fabricating and repairing articles in this mannermelts powders by feeding the power into molten material on a surfacethat has been irradiated by a laser beam. The approach is controllableand yields reproducible, precise results. In fabricating an article bythe present approach, the composition of the powder feed may bemaintained constant throughout the entire article. Alternatively, thecomposition of the powder feed may be intentionally varied within anybead or as between successive beads, to produce controllable compositionvariations throughout the article. For example, in a compressor blade, astrong, tough alloy composition may be used near the base, and a hard,wear resistant or abrasive alloy may be used near the tip.

For the repair of articles, including BLISKs, compressor blades, turbineblades, and turbine components, it is necessary only to repeat a portionof the deposition sequence from the previously described methods. Forexample, if a compressor blade breaks near the midpoint, it is necessaryonly to grind a flat surface onto the blade corresponding to the closestremaining undamaged section, and then to repeat the computer controlleddeposition of the remainder of the blade. The repaired blade isvirtually indistinguishable from the original fabricated blade, as it isaccomplished by the same apparatus and with the same shape-controllingpattern.

Often, damage to a BLISK, compressor blade, turbine blade, or turbinecomponent is in the form of uneven and irregular shaped damage. In orderto prepare the BLISK or turbine blade for repair, the damaged area maybe prepared by machining material away in the area approximate to thedamage in order to form a notch and/or to level the damaged surface.Machining away the damage is preferably conducted automatically in amulti-axis numerically controlled milling machine that is programmed toform a predetermined notch approximate to the damaged area. The repairregion is then cleaned, as needed, by aqueous cleaners and/or solvents,and dried, followed by the computer controlled deposition of theremainder of the blade. The repaired portion has no macroscopicallydetectable bond line after finishing or discontinuity to the baseportion of the blade, because the two are welded together in the samemanner employed when the blade was manufactured.

A wide variety of materials may be deposited using the approach of theinvention. For example, metals and metal alloys including titanium andtitanium alloys, nickel and nickel alloys, cobalt and cobalt alloys, andiron and iron alloys, superalloys including Ni-based, Co-based, and Febased superalloys, ceramics, cermets and plastics may be deposited.

The selection of the parameters that control the material deposition andbonding and how these parameters control deposition are critical to theability of the process to repair an article to both net or near-netshape and to full density. The parameters are transformed into commandsthat control the LNSM deposition by transfer functions.

A Laser Net Shape Manufacturing (LNSM) system is illustrated in FIG. 1.As shown in FIG. 1, a powder supply (not shown) feeds a powder nozzle 2for deposition upon a substrate 3. A laser 4 melts the powder as it isfed upon the substrate surface and also melts the substrate surface tocreate a melt pool 5 in the vicinity where the laser 4 is directed onthe powder and surface of the substrate 3. The system 1 and substrate 3are moved relatively to form a layer of a solidified deposited material7 as the melt pool 5 cools.

The path the laser 4 takes along the substrate 3 is referred to as atoolpath. The deposited material 7 is referred to as a bead of material.The width of deposited material 7 along the toolpath is referred to as abead width. The formed melt pool 5 cools and solidifies as the laser 4moves along the substrate 3. More than one powder feed may be used toform the deposited material 7, and in this illustration, a second powdernozzle 8 is shown contributing to the solidified deposited material 7.The laser 4, by melting both the powder feed and the surface of thesubstrate 3, forms a strongly bonded deposited material 7.

Upon completion of a first bead of the deposited material 7, the nozzle2 and laser 4 are positioned and moved relative to the substrate 3 sothat an adjacent second bead of deposited material 7 may be depositedalong side of the first bead, the width of the second bead overlappingthe width of the first bead. The amount of overlap may be selected to bebetween about 10% and 90%. The process is repeated until a layer of thedeposited material 7 is formed. Upon this layer, the process is repeatedto build up layers of deposited material 7 until a part is formed orrepaired.

In accordance with this invention, transfer functions were developed tocorrelate the key processing parameters including laser power, tooltravel speed, powder feed rate, and defocus distance to the fundamentaldeposition geometry of bead width. The transfer functions have beendeveloped to allow for an adaptive toolpath to be obtained by varyingthe laser power or travel speed of the laser while it is scanning alongthe tool path. In such a manner, a variable bead width of a material maybe deposited along the toolpath. The width of the deposited bead ofmaterial may be varied during a single deposition pass and during thedeposition of adjacent beads of deposited material.

The invention provides for depositing a variable bead width of amaterial of between about 0.2 mm and about 5.0 mm, and preferablybetween about 0.76 mm and about 1.52 mm, and most preferably betweenabout 0.89 mm and about 1.42 mm. The range of variable bead widthdeposited within a layer depends upon deposition parameters includingthe deposited material composition and the geometry of the formedarticle.

By applying this method, a constant bead overlap ratio between adjacentbeads of deposited material can be achieved that effectively eliminatesfusion imperfections. The inventors have determined that a constantoverlap ratio selected from about 10% to about 90% leads to improvedbuild up performance. Furthermore, the inventors have determined that byusing a variable bead width in a layer of about 0.76 mm to about 1.52mm, improved deposition quality can be achieved that effectivelyeliminates gaps in the deposited material.

Adaptive bead width deposition with constant overlap ratio when appliedto overhanging regions produces built up layers that are free of surfacerippling. Overhanging regions are typically considered areas with a leanangle of approximately less than 35 degrees with respect to vertical. Inthese regions, a larger melt pool is needed to have higher powdercapture efficiency, so that the deposit layer has enough material tosupport the next layer without slumping.

Adaptive toolpath deposition solves the prior art problems associatedwith depositing material upon a cold substrate. This novel method allowsfor the ramping down the laser power over the built up layers to ensurea constant bead width when depositing the first several layers on a coldsubstrate. Additionally, the power may be ramped down during thedeposition of the last several layers close to the narrow tip of theblade. Particularly, an initial high laser power is selected and rampeddown to a constant laser power over the first 2 to 100 depositedmaterial layers to a determined constant laser power. This determinedconstant laser power is used to deposit the successive material layersuntil the final material layers are to be deposited. For the depositionof the final material layers, the laser power is ramped down again.Preferably, the laser is ramped down for the last 3 to 100 layers closeto a narrow tip or at the surface of the newly fabricated or repairedpart or blade. It should be noted that the number or layers are providedfor illustrative purposes and do not represent the limits of the presentinvention. The range of layers over which adjustments to the laser powerare made depends on the geometry of the substrate and the thermophysicalproperties of the substrate and powder material.

When designing the tool path for BLISK repair, the toolpath overlapratio and overhanging angle at every interpolate point are calculatedaccording to the part solid model. This information is then converted tolaser power or speed commands at appropriate sections of tool pathG-codes according to the transfer functions.

This method enables the near net shape fabrication or repair of a BLISKblades that saves material and labor for post-machining process. BecauseLNSM is capable of fabricating and restoring the complete blade, evenmore severely damaged blades can be repaired.

FIG. 2 shows perspective view of a BLISK 10. The BLISK 10 is formed ofBLISK blades 20 and a BLISK compressor disk 30. In a specific embodimentof the invention, the BLISK 10 may be repaired by replacing damagedmaterial of the BLISK blades 20. Additionally, in a second specificembodiment of the invention, a BLISK may be manufactured by formingBLISK blades 20 upon the BLISK compressor disk 30.

FIG. 3 illustrates in block diagram form a specific embodiment of themethod for repairing a BLISK. The method included determining initialprocess parameters that were input into a controller comprised of adigital computer that directed movement of a deposition zone along atool path and provided control signals to adjust apparatus functionssuch as laser power and the speed of the laser beam, such as the speedat which a deposition head moved the laser beam and the rate at whichpowder was provided to the deposition zone moving along the toolpath.

As shown in FIG. 3, the initial parameters included, but were notlimited to laser power, laser scanning velocity, powder feed rate, andoverlap ratio. These initial parameters were provided to the controller,and the programmed transfer functions then determined the basicdeposition feature of bead width and height corresponding to the desiredposition within the geometry of the desired formed material. The layerdata were converted to tool path data in terms of computer numericalcontrol (CNC) G-codes. These codes were then utilized to drive thefabrication tool for building up the deposited material layers.

In accordance with a specific embodiment of the invention as shown inFIG. 4, a damaged compressor blade 320 was repaired. As shown in FIG. 4,a compressor blade 320 contains damaged material 340. Damaged material340 was removed to an approximately flat surface 350. The damagedmaterial 340 was removed by grinding, although other methods of materialremoval may be used. The damaged component is shown as compressor blade320, but it may be a damaged blade of a BLISK.

As shown in FIG. 5, the compressor blade 420 had layers of material 460built up upon the flat substrate 450 after the damaged material had beenremoved to repair the compressor blade 420. In this specific embodiment,the material 460 was a nickel-based superalloy Inconel 718, also knownas IN718. The material 460 was deposited according to the inventivemethod as outlined in FIG. 2, and as further disclosed herein. Thepractice of the invention resulted in a repair of the compressor blade430 to a net shape form without the need for additional machining afterthe repair. It should be understood that the material 460 is not limitedto the specific embodiment, but may be selected from known structuralmaterials in the field of the invention.

By depositing a variable bead width along the toolpath at a constantoverlap ratio, the lack-of-fusion imperfections in the solid depositwere effectively reduced. In this specific embodiment, a variable beadwidth of between about 0.89 mm and about 1.42 mm and an overlap ofapproximately 50 percent was used to repair the compressor blade 420 anda bead deposit was formed that was substantially free of imperfections,including gap imperfections and porosity.

The power control at the overhanging regions solved the prior artsurface rippling problem on the built up compressor blade surface. Thesurface roughness of the built up compressor blade 420 was improved byusing slightly higher laser power and slower speed for the exteriorcontour tool path compared to the interior stitching tool path.

The current invention allowed for the ramping down of laser power overthe built up layers allowing for a deposit of a variable bead width andheat dissipation rate in the built up material of the compressor blade420. This reduced problems such as lack of fusion at the initial layerswhen depositing on the cold surface 450. Additionally, by adaptivelyramping down the laser power over the layers as approaching the narrowtip of the compressor blade 420, thicker bead width and surfaceoxidation due to overheating was minimized.

In addition, a single variable bead width of deposited material may forma layer. In such a manner, layers formed of a single variable bead widthof deposited material may be deposited upon layers formed of multipleadjacent beads of material. Furthermore, a part may be fabricated byforming layers of single bead widths upon layers formed of a single beadwidth of a deposited material to form or repair a part.

In accordance with a second specific embodiment of the invention, aBLISK 10 as shown in FIG. 2 was manufactured. According to thisembodiment, a BLISK compressor disk 30 was formed by the conventionalfabrication method of casting, although the disks may be formed by othermethods such as forging or machining. An outer surface of the BLISKcompressor disk 30 provided the substrate for the BLISK blades 20 to beformed thereupon.

A BLISK blade material, in this case a nickel-based superalloy Inconel718, also known as IN718, was used to form BLISK blades 20 upon theBLISK compressor disk 30. The IN718 material was deposited according tothe inventive method as outlined in FIG. 2, and as further disclosedherein. The practice of the invention resulted in fabrication of theBLISK blades 20 to a net shape form without the need for additionalmachining after the fabrication.

By depositing a variable bead width along the toolpath at a constantoverlap ratio, the lack-of-fusion imperfections in the solid depositwere effectively reduced. In this specific embodiment, a variable beadwidth in a layer of between about 0.89 mm to about 1.42 mm and anoverlap of approximately 50 percent were used to fabricate BLISK blades20 that were substantially free of imperfections, including gapimperfections.

The power control at the overhanging regions solved the prior artsurface rippling problem on the build up BLISK blades 20 surface. Thesurface roughness of the built up BLISK blades 20 was improved by usingslightly higher laser power and slower speed for the exterior contourtool path compared to the interior stitching tool path.

The current invention allowed for the ramping down of laser power overthe built up layers allowing for a deposit of a variable bead width andheat dissipation rate in the built up part. This reduced problems suchas lack of fusion imperfections at the initial layers when depositing onthe cold substrate of the surface of the BLISK compressor disk 30.Additionally, by adaptively ramping down the laser power over the layersas approaching the narrow tip of the BLISK blades 20, surface oxidationdue to overheating was minimized.

The performance of the BLISK is not reduced as a result of a repairaccording to the invention. This approach allows the blades of the BLISKto be repaired multiple times, without loss of the functionality of theBLISK due to an excessive reduction in its dimensions in thenon-repaired regions to below the minimum specified values.

This method can be applied to new part buildup as well as repair. In newpart buildup, the initial layers are deposited upon a sacrificialsubstrate, or, as when forming a BLISK, material buildup may beperformed on an integrated section of the part such as the BLISKcompressor disk. The adaptive control of the toolpath for the initiallayers, overhanging regions and edge regions is the same as in therepair application.

The disclosed invention presents many advantages over the prior artmethod of layered deposition. First, by depositing a variable bead widthalong the tool path at a constant overlap ratio, the number of lack offusion imperfections in the solid deposit can be reduced. Second, thepower control at the overhanging regions can solve the surface ripplingproblem on the build up blade surface by more effective control ofheating at these regions. Third, the use of a higher laser power andslower speed for the exterior contour tool path compared with theinterior stitching tool path improves the surface roughness of thedeposited material. Fourth, by ramping down the laser power over thebuilt up layers, a constant bead width and heat dissipation rate can bemaintained in the built up part. Problems such as lack of fusion andporosity at the initial few layers when depositing on a “cold” substrateand surface oxidation due to overheating when depositing close to thenarrow blade tip are solved by adaptively ramping down the laser powderover the deposited layers.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

The invention claimed is:
 1. A method for laser cladding a substrate,comprising: providing the substrate; inputting transfer functions into acomputer to control parameters comprising laser power, laser velocity,defocus distance and powder feed rate to obtain an approximate constantvariable bead width of deposited material and overlap ratio; depositinga first determined variable bead width of a material along a toolpathupon the substrate; depositing a second adjacent determined variablebead width of a material along the toolpath which overlaps the firstdetermined variable bead width of deposited material, wherein the stepof depositing the second adjacent determined variable bead widthincludes varying the laser power to provide varying of the secondadjacent determined variable bead width along the tool path such that anoverlap between the first determined variable bead width and the secondadjacent determined variable bead width is held approximately constant;continuing to deposit a plurality of overlapping predetermined adjacentvariable bead widths of a material until a first material layer iscomplete; forming a second material layer by depositing a plurality ofoverlapping predetermined variable bead widths of a material on top ofthe first material layer; and continuing to deposit material layers ontop of deposited material layers until the cladding is complete; whereinthe variable bead width of the deposited material is controlled by thecomputer having a plurality of input parameters to maintain theapproximately constant percent of bead width overlap; and wherein thelaser power is initially a higher laser power for a first 2 to 100deposited powder layers, then ramped down over the course of depositingthe remaining powder layers.
 2. The method of claim 1, wherein eachdeposited variable bead width of a material in a layer is varied betweenabout 0.2 mm and about 5.0 mm.
 3. The method of claim 1, wherein theoverlap is maintained between about 10% to about 90%.
 4. A laser netshape manufacturing or repair method, comprising: providing a substrate;inputting transfer functions into a computer to control parameterscomprising laser power, laser velocity, defocus distance and powder feedrate to obtain an approximate constant variable bead width of depositedmaterial and overlap ratio; forming by laser cladding a first determinedvariable bead width of a material along a toolpath upon the substrate;forming by laser cladding a second adjacent determined variable beadwidth of a material along the tool path which overlaps the firstdetermined variable bead width, wherein the step of forming the secondadjacent determined variable bead width includes varying the laser powerto provide varying of the second adjacent determined variable bead widthalong the tool path such that an overlap between the first determinedvariable bead width and the second adjacent determined variable beadwidth is held approximately constant; continuing to deposit overlappingpredetermined adjacent variable bead widths of a material until a firstpowder layer is complete; forming by laser cladding a second powderlayer by depositing overlapping predetermined variable bead widths of amaterial on top of the first powder layer; and continuing to depositpowder layers on top of deposited material layers until the cladding iscomplete and a net shape article is manufactured or repaired; whereinthe variable bead width of the deposited material is controlled by thecomputer having input parameters to maintain an approximately constantpercent of bead width overlap; and wherein the laser power is initiallya higher laser power for a first 2 to 100 deposited powder layers, thenramped down over the course of depositing the remaining powder layers.5. The laser net shape manufacturing method of claim 4, wherein eachformed variable bead with is varied between about 0.2 mm and about 5.0mm in a layer.
 6. The laser net shape manufacturing method of claim 4,wherein the overlap is between about 10% to about 90%.
 7. A method ofrepairing a BLISK, compressor blade, turbine blade or turbine component,comprising: providing a damaged BLISK, compressor blade, turbine bladeor turbine component; prepping the damaged BLISK, compressor blade,turbine blade or turbine component to form a substrate surface;inputting transfer functions into a computer to control parameterscomprising laser power, laser velocity, defocus distance and powder feedrate to obtain an approximate constant variable bead width of depositedmaterial and overlap ratio; depositing a first determined variable beadwidth of a material along a toolpath upon the substrate surface;depositing a second determined variable bead width of a material along atoolpath that is adjacent the deposited first determined variable beadwidth of a material and overlaps the first determined variable beadwidth of the deposited material layer, wherein the step of depositingthe second determined variable bead width includes varying the laserpower to provide varying of the second determined variable bead widthalong the tool path such that an overlap between the first determinedvariable bead width and the second determined variable bead width isheld approximately constant; continuing to deposit adjacent overlappingpredetermined variable bead widths of a material until a first materiallayer is complete; forming a second material layer by depositingoverlapping predetermined variable bead widths of a material on top ofthe first material layer; and continuing to deposit material layers ontop of deposited material layers until the cladding is complete; whereinthe bead width of the deposited material is controlled by the computerhaving input parameters to maintain an approximate constant percent ofvariable bead width overlap of adjacent variable bead widths ofmaterial; wherein each deposited variable bead with is varied betweenabout 0.2 mm and about 5.0 mm in a layer; and wherein the laser power isinitially a higher laser power for a first 2 to 100 deposited powderlayers, then ramped down over the course of depositing the remainingpowder layers.
 8. The method of repairing the BLISK, compressor blade,turbine blade or turbine component of claim 7, wherein the overlap isbetween about 10% and about 90%.